In the computing industry in general, the trend is to make products smaller, faster, and better. Likewise, the trend in the semiconductor industry is to shrink packaging requirements for integrated circuit (IC) devices. Accordingly, variations in packaging techniques have evolved.
A semiconductor IC packaged device generally includes an IC chip (die) being connected to inner leads of a lead frame by wire bonds. The chip, wire bonds, and inner leads are completely encapsulated for protection with a substance, such as plastic. Outer leads communicate with the inner leads of the lead frame, but the outer leads typically remain exposed for mounting of the packaged device to some other external circuitry, such as a printed circuit board.
In a conventional IC packaged device, a semiconductor die is placed on and bonded to a center die paddle of a lead frame for support. Inner lead fingers of the lead frame approach the paddle but do not contact or communicate with the paddle. Rather, wire bonds communicate between contact pads on the die and the inner lead fingers of the lead frame by spanning the gap between the die and the fingers. The wire bonds allow for the transmission of the electrical signals to and from the die and the lead frame.
To shrink the conventional packaging requirements, techniques such as the Lead On Chip (LOC) method have been developed. The LOC technique disposes the inner lead fingers of a lead frame directly over the die (or IC chip) rather than away from the die. Double-sided adhesive insulating tape attaches the conductive lead fingers to the die so that no gap exists between the die and lead fingers. The wire bonds generally communicate between contact pads on the die and the inner lead fingers which are disposed directly over a portion of the die adjacent the die pads. The tape is subsequently cured to a hardened state wherein the lead fingers are fixedly attached thereto.
This LOC technique allows the entire packaging of the IC device to be smaller. Similar to LOC, other variations of using an adhesive tape for shrinking packaging requirements include a Tape Under Frame technique and a Leads Under Die method.
Although IC packaging is minimized in each of these packaging techniques that uses an adhesive tape, other problems surface. One such problem is obtaining a good solid bond between the lead finger and the tape. Another is lead finger .music-flat.bounce." Finger bounce occurs during wire bonding when the wire must be bonded from the die pad to the inner lead finger. As the lead finger is heated during placing of the wire bond, the adhesive tape communicating with the finger also heats up. Consequently, the tape softens up and causes the finger to no longer remain solidly attached and immovable. This softening of the tape, in conjunction with the pressure applied in placing the wire bond, causes the lead finger to .music-flat.bounce" and lose its grip with the tape, making it difficult to obtain a good solid bond.
Given the foregoing problems associated with lead frames, lead fingers, and adhesive tape in lead package systems, objects of the present invention are to provide a semiconductor lead package system having improved lead finger adherence to adhesive tape.